How may coins did you by? It doesn't take a mathematics graduate, or even a HS graduate to tell you that any kind of trading is risky, and you shouldn't be investing beyond what you are prepared to lose. Make sure you understand your risk, and are really prepared to take it. While I don't think this is probable, it is possible that the price of BTC could bleed slowly (or quickly) down to pennies.

You don't explain it to your mother. If you must explain it, then leave out almost everything and tell her a really really short version like: it's virtual money. You could then add more details : it is not owned by any government, but by the users, it has low fees, etc. I wouldn't talk about mining nor anything like that. It's too confusing.

That being said, any investment in bitcoins is dangerous. It's high risk.

Bitcoin will not be used by everyone. In fact, it won't be used by the vast majority of people. It's an online currency that exists as an alternative to paper money. It can grow (I surely hope so), but it will never replace dollar, nor euro, nor any other real currency.

1. don't talk about mining. its confusing.2. don't talk about the blockchain. its even more confusing.3. say that bitcoin is "digital gold". that'll definitely make them sit up.4. say that only a fixed number will be issued and then NO MORE.5. say that since its digital it can be instantaneously transported across borders w/o detection. they'll immediately realize the implications of this.6. don't say anything about "cryptocurrency" or "cryptography". this makes it sound like bitcoin is trying to hide something along the likes of Silk Road and other illegal activities.7. say that bitcoins are secured by "advanced mathematical algorithms" that prevent counterfeiting. sounds impressive.8. try to avoid saying anything about Satoshi since an unknown character brings to mind a shady type character or hidden agenda.9. do explain that the decentralized or "spread out" nature of bitcoin computers makes it indestructable to gov't or Fed intervention. they'll like that.10. when they ask what its denominated in say that bitcoin is a currency UNTO ITSELF and "floats" in value against other fiat currencies like the USD but bitcoin is in fact NOT a fiat currency. you might mention that you think that bitcoin will become the gold std against which all other currencies will be measured.